Process for removal of poisonous gases

ABSTRACT

Hydrides of As, B, P, Sb or Se in a gas can easily be removed from the gas by contacting the gas with an adsorbent comprising activated carbon having (1) iodine and/or one or more kinds of iodine compounds and/or (2) one or more kinds of sulfates and nitrates of NH 4 , Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Sn supported thereon.

This invention relates to a process of treating poisonous gasescontaining hydrides of B, P, As, Sb and Se.

Hydrides, such as B₂ H₆, PH₃, AsH₃, SbH₃ and H₂ Se, are utilized inlarge quantities for raw material gases for production ofsemiconductors, fumigation gases, etc., but even in trace amounts, areextremely poisonous to the human body. Therefore, the development of amethod capable of efficiently removing these hydrides in gas is stronglydemanded.

As a method of removing hydrides of B, P, As, Sb and Se, there have beenproposed, for example, a procedure of washing with chemical solutionssuch as oxidizing solutions, or an adsorption process with use ofadsorbents composed mainly of ferric chloride. However, these methodsshow inferior removal effect and pose problems.

The present inventors, in view of these circumstances, conductedintensive investigation, and as a result, found that by using activatedcarbon with iodine, iodine compounds and sulfates and nitrates of NH₄,Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Sn, supportedthereon hydrides of B, P, As, Sb and Se in gases can be removed highlyefficiently, which has culminated in the present invention.

Thus, the present invention is concerned with:

A process of removing one or more kinds of hydrides of As, B, P, Sb orSe from a gas containing one or more kinds of hydrides of As, B, P, Sbor Se, which comprises contacting said gas with an adsorbent comprisingactivated carbon having (1) iodine and/or one or more kinds of iodinecompounds (hereinafter referred to in some instances as "FirstComponent") and/or (2) one or more kinds of sulfates and nitrates ofNH₄, Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Sn(hereinafter referred to in some instances as "Second Component")supported thereon.

The activated carbon which is useful in the present invention may be anytype of activated carbon produced by the known processes from coal,coke, wood charcoal, coconut shells, resins, etc., while its specificsurface area is preferably within the range from 200 to 2000 m² /g. Withreference to its shape and form, use is suitably made for example ofspherical- and cylindrical-formed, crushed, powdered and fibrous-formedactivated carbon according to the type of gas treatment methods.

Specific examples of the First Component useful in the presentinvention, include iodides, such as LiI, NaI, KI, RbI, CsI, BeI₂, MgI₂,CaI₂, SrI₂, BaI₂, NH₄ I and HI, iodic acid and its salts, such as HIO₃,NH₄ IO₃, NaIO₃ and KIO₃, periodic acid and its salts, such as HIO₄, NH₄IO₄, NaIO₄ and KIO₄, and iodine oxides, such as I₂ O₅ and IO₂.

Specific examples of the Second Component, which is utilizable, include(NH₄)₂ SO₄, Ag₂ SO₄, Al₂ (SO₄)₃, Ti₂ (SO₄)₃, VOSO₄, Cr₂ (SO₄)₃, MnSO₄,FeSO₄, Fe₂ (SO₄)₃, CoSO₄, NiSO₄, CuSO₄, ZnSO₄, CdSO₄, PbSO₄, SnSO₄, NH₄NO₃, AgNO₃, Al(NO₃)₃, Cr(NO₃)₃, Mn(NO₃)₂, Fe(NO₃)₂, Fe(NO₃)₃, Co(NO₃)₂,Ni(NO₃)₂, Cu(NO₃)₂, Zn(NO₃)₂, Cd(NO₃)₂, Pb(NO₃)₂, etc.

The adsorbent used in the present invention, which comprises activatedcarbon having each of the components being supported thereon, can beproduced by impregnating or spraying activated carbon with a solution orsuspension of the individual components in water (inclusive of aqueousacid or alkali solutions) or various solvents (e.g., alcohols, such asmethanol and ethanol, ketones, such as acetone and methyl ethyl ketone,etc.), and if necessary, by drying the impregnated or sprayed activatedcarbon at a temperature of not higher than about 130° C. or calcining ata temperature of not lower than 130° C.

In cases in which not less than two components are deposited onactivated carbon, the components may be supported simultaneously or maybe supported individually, whereby they may be supported in arbitraryorder.

The supported amounts of each of the First and Second Components inactivated carbon are 1 mg to 500 mg per g of activated carbon (0.5 mg to250 mg for silver sulfate and silver nitrate), preferably 5 to 400 mg (1to 150 mg for silver sulfate and silver nitrate).

The present invention is usually carried out by contacting a gascontaining hydrides of B, P, As, Sb and Se with the adsorbent in thepresence of oxygen.

The contact temperature is not higher than 150° C., preferably -10° to120° C., more preferably 0° to 100° C., and the contact pressure is notmore than 10 atm., preferably 0.01 to 5 atm., with the contact timebeing 1/20 to 100 seconds as converted at 25° C. and 1 atm., preferably1/10 to 50 seconds.

If oxygen is not contained in the gas to be treated, it is preferable toadd oxygen to the gas. The amount of oxygen contained in the gas isusually not less than one mol per mol of hydrides of B, P, As, Sb andSe, preferably not less than 2 mol.

The contacting of the adsorbent with a gas containing hydrides of B, P,As, Sb and Se can be conducted for example by use of fixed bed, movingbed and fluidized bed.

The examples are described below to illustrate the present inventionmore specifically.

EXAMPLE 1

Activated carbon A₀ of 16 to 24 mesh having a BET specific surface areaof 1,150 m² /g was sprayed uniformly with aqueous solutions orsuspensions of the required amounts of iodine, iodine compounds and/orsulfates and nitrates of NH₄, Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Cd, Pb and Sn, and then dried at 110° C.

15 ml each of the various adsorbents thus obtained were packed intocolumns of 1.6 cm in diameter made of glass, respectively, and theatmospheric air (with relative humidity of 60%) of 30° C. containing 15ppm of AsH₃ and 15 ppm of PH₃ was passed through the respective columnsat a linear flow rate of 40 m/sec to conduct the individual adsorptionbreak-through tests for AsH₃ or PH₃, whereby the removal ratios for AsH₃or PH₃ at each of the determined times were measured. The results are asshown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________             The first                                                                             The second                                                                            Percent removal of AsH.sub.3                                                                Percent removal of PH.sub.3                     component and                                                                         component and                                                                         at the elapsed time                                                                         at the elapsed time shown              Adsorbent                                                                              its amount                                                                            its amount                                                                            shown below (%)                                                                             below (%)                              No.      (mg/g)  (mg/g)  5 hrs.                                                                            10 hrs.                                                                            30 hrs.                                                                            5 hrs.                                                                             10 hrs.                                                                            30 hrs.                      __________________________________________________________________________    A.sub.0 (Control)                                                                      0       0       35  5    0    4    0    0                            A.sub.1 (The present                                                                   LiI-50  0       100 85   68   93   61   40                           invention)                                                                    A.sub.2 (The present                                                                   NaI-50  0       100 88   70   91   65   47                           invention)                                                                    A.sub.3 (The present                                                                   KI-50   0       100 100  100  100  100  100                          invention)                                                                    A.sub.4 (The present                                                                   MgI.sub.2 -50                                                                         0       100 80   64   98   61   35                           invention)                                                                    A.sub.5 (The present                                                                   BaI.sub.2 -50                                                                         0       100 85   73   90   65   41                           invention)                                                                    A.sub.6 (The present                                                                   NH.sub.4 I-50                                                                         0       100 100  96   95   90   80                           invention)                                                                    A.sub.7 (The present                                                                   NaIO.sub.3 -50                                                                        0       100 100  100  100  85   64                           invention)                                                                    A.sub.8  (The present                                                                  KIO.sub.3 -50                                                                         0       100 100  100  100  100  100                          invention)                                                                    A.sub.9 (The present                                                                   I.sub.2 -50                                                                           0       100 100  100  100  100  100                          invention)                                                                    A.sub.10 (The present                                                                  I.sub.2 O.sub.5 -50                                                                   0       100 100  100  100  100  100                          invention)                                                                    A.sub.11 (The present                                                                  HIO.sub.3 -50                                                                         0       100 100  100  100  100  98                           invention)                                                                    A.sub.12 (The present                                                                  KI-5    0       90  85   61   88   71   50                           invention)                                                                    A.sub.13 (The present                                                                  KI-25   0       100 100  100  100  100  90                           invention)                                                                    A.sub.14 (The present                                                                  KI-400  0       100 100  100  100  100  100                          invention)                                                                    B.sub.1 (The present                                                                   0       (NH.sub.4).sub.2 SO.sub.4 -50                                                         96  93   84   90   85   60                           invention)                                                                    B.sub.2 (The present                                                                   0       AgNO.sub.3 -5                                                                         100 98   90   98   85   53                           invention)                                                                    B.sub.3 (The present                                                                   0       Al(NO.sub.3).sub.3 -50                                                                85  60   30   82   60   48                           invention)                                                                    B.sub.4 (The present                                                                   0       Ti.sub.2 (SO.sub.4).sub.3 -50                                                         81  48   23   80   55   31                           invention)                                                                    B.sub.5 (The present                                                                   0       VOSO.sub.4 -50                                                                        98  83   53   87   65   43                           invention)                                                                    B.sub.6 (The present                                                                   0       Cr(NO.sub.3).sub.3 -50                                                                88  65   43   75   50   32                           invention)                                                                    B.sub.7 (The present                                                                   0       MnSO.sub.4 -50                                                                        98  85   61   83   45   21                           invention)                                                                    B.sub.8 (The present                                                                   0       FeSO.sub.4 -50                                                                        100 100  95   92   80   65                           invention)                                                                    B.sub.9 (The present                                                                   0       Fe(NO.sub.3).sub.3 -50                                                                100 100  91   100  90   75                           invention)                                                                    B.sub.10 (The present                                                                  0       CoSO.sub.4 -50                                                                        98  85   73   85   72   60                           invention)                                                                    B.sub.11 (The present                                                                  0       Ni(NO.sub.3).sub.2 -50                                                                95  60   35   83   65   53                           invention)                                                                    B.sub.12 (The present                                                                  0       CuSO.sub.4 -50                                                                        100 98   71   93   82   61                           invention)                                                                    B.sub.13 (The present                                                                  0       Zn(NO.sub.3).sub.2 -50                                                                95  80   63   83   60   46                           invention)                                                                    B.sub.14 (The present                                                                  0       CdSO.sub.4 -50                                                                        97  78   68   80   64   41                           invention)                                                                    B.sub.15 (The present                                                                  0       Pb(NO.sub.3).sub.2 -50                                                                98  83   60   93   72   51                           invention)                                                                    B.sub.16 (The present                                                                  0       SnSO.sub.4 -50                                                                        100 95   70   95   68   43                           invention)                                                                    B.sub.17 (The present                                                                  0       Fe.sub.2 (SO.sub.4).sub.3 -50                                                         100 95   90   100  75   47                           invention)                                                                    __________________________________________________________________________             The first                                                                             The second                                                                            Percent removal of AsH.sub.3                                                                Percent removal of PH.sub.3                     component and                                                                         component and                                                                         at the elapsed time shown                                                                   at the elapsed time shown              Adsorbent                                                                              its amount                                                                            its amount                                                                            below (%)     below (%)                              No.      (mg/g)  (mg/g)  50 hrs.                                                                           100 hrs.                                                                           200 hrs.                                                                           50 hrs.                                                                            100 hrs.                                                                           200 hrs                      __________________________________________________________________________    C.sub.1 (The present                                                                   NaI-50  AgNO.sub.3 -50                                                                        100 100  100  100  100  100                          invention)                                                                    C.sub.2 (The present                                                                   KI-50   Ti.sub.2 (SO.sub.4).sub.3 -50                                                         100 100  85   100  98   79                           invention)                                                                    C.sub.3 (The present                                                                   MgI-50  Cr(NO.sub.3).sub.3 -50                                                                100 98   90   100  83   70                           invention)                                                                    C.sub.4 (The present                                                                   I.sub.2 O.sub.5 -50                                                                   Co(NO.sub.3).sub.2 -50                                                                100 100  100  100  100  100                          invention)                                                                    C.sub.5 (The present                                                                   NH.sub.4 I-50                                                                         SnSO.sub.4 -50                                                                        100 100  85   100  100  81                           invention)                                                                    C.sub.6 (The present                                                                   KI-50   Ag.sub.2 SO.sub.4 -5                                                                  100 100  88   100  100  100                          invention)                                                                    C.sub.7 (The present                                                                   KI-50   VOSO.sub.4 -50                                                                        100 100  100  100  100  100                          invention)                                                                    C.sub.8 (The present                                                                   KI-50   Cr.sub.2 (SO.sub.4).sub.3 -50                                                         100 100  100  100  100  100                          invention)                                                                    C.sub.9 (The present                                                                   KI-50   Mn(NO.sub.3).sub.2 -50                                                                100 100  100  100  100  100                          invention)                                                                    C.sub.10 (The present                                                                  KI-50   Fe(NO.sub.3).sub.2 -50                                                                100 100  100  100  100  100                          invention)                                                                    C.sub.11 (The present                                                                  KI-50   Co(NO.sub.3).sub.2 -50                                                                100 100  100  100  100  100                          invention)                                                                    C.sub.12 (The present                                                                  KI-50   Cu(NO.sub.3).sub.2 -50                                                                100 100  100  100  100  100                          invention)                                                                    C.sub.13 (The present                                                                  KI-50   ZnSO.sub.4 -50                                                                        100 100  100  100  100  100                          invention)                                                                    C.sub.14 (The present                                                                  NH.sub.4 I-50                                                                         FeSO.sub.4 -50                                                                        100 100  100  100  100  100                          invention)                                                                    C.sub.15 (The present                                                                  BaI-50  FeSO.sub.4 -50                                                                        100 100  80   100  100  89                           invention)                                                                    C.sub.16 (The present                                                                  I.sub.2 -5                                                                            FeSO.sub.4 -10                                                                        100 100  100  100  100  100                          invention)                                                                             KI-10                                                                C.sub.17 (The present                                                                  I.sub.2 -5                                                                            FeSO.sub.4 -10                                                                        100 100  100  100  100  100                          invention)                                                                             NH.sub.4 I-10                                                        D.sub.1 (The present                                                                   KI-5    FeSO.sub.4 -50                                                                        100 98   65   100  88   60                           invention)                                                                    D.sub.2 (The present                                                                   KI-10   FeSO.sub.4 -50                                                                        100 100  79   100  100  81                           invention)                                                                    D.sub.3 (The present                                                                   KI-50   FeSO.sub.4 -50                                                                        100 100  100  100  100  100                          invention)                                                                    D.sub.4 (The present                                                                   KI-50   FeSO.sub.4 -5                                                                         100 100  83   100  100  84                           invention)                                                                    D.sub.5 (The present                                                                   KI-50   FeSO.sub.4 -10                                                                        100 100  100  100  100  100                          invention)                                                                    D.sub.6 (The present                                                                   KI-5    FeSO.sub.4 -5                                                                         100 85   77   100  78   61                           invention)                                                                    D.sub.7 (The present                                                                   KI-5    Fe.sub.2 (SO.sub.4).sub.3 -50                                                         100 93   81   100  96   86                           invention)                                                                    D.sub.8 (The present                                                                   KI-10   Fe.sub.2 (SO.sub.4).sub.3 -50                                                         100 100  93   100  100  85                           invention)                                                                    D.sub.9 (The present                                                                   KI-50   Fe.sub.2 (SO.sub.4).sub.3 -5                                                          100 100  95   100  100  83                           invention)                                                                    D.sub.10 (The present                                                                  KI-50   Fe.sub.2 (SO.sub.4).sub.3 -10                                                         100 100  98   100  100  100                          invention)                                                                    D.sub.11 (The present                                                                  KI-5    Fe.sub.2 (SO.sub.4).sub.3 -5                                                          100 93   75   100  90   71                           invention)                                                                    D.sub.12 (The present                                                                  KI-5    Fe.sub.2 (SO.sub.4).sub.3 -50                                                         100 90   68   100  79   57                           invention)                                                                    D.sub.13 (The present                                                                  KI-5    FeSO.sub.4 -250                                                                       100 95   73   100  88   70                           invention)                                                                    D.sub.14 (The present                                                                  KI-250  FeSO.sub.4 -5                                                                         100 100  100  100  100  100                          invention)                                                                    __________________________________________________________________________

EXAMPLE 2

Packed into columns of 1.6 cm in diameter made of glass were 20 ml eachof A₀, A₃, A₆, A₁₀, A₁₁, B₂, B₇, B₈, B₁₁, C₁, C₇, C₁₂, C₁₄, C₁₇, D₃, D₈and D₁₃ set forth in the above Table 1, and the atmospheric air (withrelative humidity of 60%) of 30° C. containing 10 ppm of B₂ H₆, 10 ppmof H₂ Se or 10 ppm of SbH₃ was passed through the respective columns ata linear flow rate of 30 cm/sec to conduct the individual break-throughadsorption tests for B₂ H₆, H₂ Se or SbH₃, whereby the lengths of timeuntil B₂ H₆, H₂ Se or SbH₃ leaked out of the respective columns, (i.e.,the lengths of time required until the respective removal ratios reached95 %) were determined. The results are shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________             The length of time for which                                                                The length of time for which                                                                The length of time for which                      the removal percentages                                                                     the removal percentages                                                                     the removal percentages                  Adsorbent                                                                              for B.sub.2 H.sub.6 reached 95%                                                             for H.sub.2 Se reached 95%                                                                  for SbH.sub.3 reached                    __________________________________________________________________________                                         95%                                      A.sub.0 (Control)                                                                      1/6           1/4           1/3                                      A.sub.3 (The present                                                                   63            41            55                                       invention)                                                                    A.sub.6 (The present                                                                   43            40            48                                       invention)                                                                    A.sub.10 (The present                                                                  75            78            80                                       invention)                                                                    A.sub.11 (The present                                                                  30            28            30                                       invention)                                                                    B.sub.2 (The present                                                                   19            30            45                                       invention)                                                                    B.sub.7 (The present                                                                   25            19            24                                       invention)                                                                    B.sub.8 (The present                                                                   21            20            20                                       invention)                                                                    B.sub.11 (The present                                                                  28            32            19                                       invention)                                                                    C.sub.1 (The present                                                                   153           198           185                                      invention)                                                                    C.sub.7 (The present                                                                   258           250           233                                      invention)                                                                    C.sub.12 (The present                                                                  218           200           223                                      invention)                                                                    C.sub.14 (The present                                                                  300           310           305                                      invention)                                                                    C.sub.17 (The present                                                                  313           300           320                                      invention)                                                                    D.sub.3 (The present                                                                   355           368           390                                      invention)                                                                    D.sub.8 (The present                                                                   370           373           398                                      invention)                                                                    D.sub.13 (The present                                                                  195           210           195                                      invention)                                                                    __________________________________________________________________________

What is claimed is:
 1. A process of removing one or more hydridesselected from the group consisting of hydrides of As, B, P, Sb and Sefrom a gas containing oxygen and one or more of said hydrides, whichcomprises contacting said gas with an adsorbent comprising activatedcarbon having (1) iodine and/or one or more iodine compounds and/or (2)one or more members selected from the group consisting of sulfates andnitrates of NH₄, Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb andSn supported thereon.
 2. A process as claimed in claim 1, wherein theadsorbent is one comprising activated carbon having (1) 1 to 500 mg ofiodine and/or one or more iodine compounds and/or (2) 1 to 500 mg of oneor more members selected from the group consisting of sulfates andnitrates of NH₄, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, and Snsupported thereon, per g of activated carbon.
 3. A process as claimed inclaim 1, wherein the adsorbent is one comprising activated carbon having(1) 1 to 500 mg of iodine and/or one or more iodine compounds and/or (2)0.5 to 250 mg of one or more members selected from the group consistingof sulfate and nitrate of Ag supported thereon, per g of activatedcarbon.
 4. A process as claimed in claim 1, wherein the adsorbent is onecomprising activated carbon having iodine and potassium iodide supportedthereon.
 5. A process as claimed in claim 1, wherein the adsorbent isone comprising activated carbon having potassium iodide and ferroussulfate supported thereon.
 6. A process as claimed in claim 1, whereinthe gas is contacted with the activated carbon at a temperature of nothigher than 150° C.